New Variety Of Rice Fights Global Warming And Global Hunger

A slight change in a single gene of rice can avoid the same amount of greenhouse gas emissions each year as all the wind turbines in the world, the same as 15 nuclear power plants. Work led by Dr. Christer Jansson at the Department of Energy’s Pacific Northwest National Laboratory found that transferring one gene from barley to rice lowered the methane (CH4 or natural gas) emissions from rice paddies to almost zero.

As the COP21 climate change talks get underway today in Paris, it’s nice to see real progress on a critical front that doesn’t get enough attention – food and climate.

Agriculture is a primary source of greenhouse gas emissions, especially as humans practice it nowadays, and emissions are on the rise. Over the last ten years, agriculture, forestry and other land uses have emitted over 10 billion tons of carbon dioxide-equivalent/year:

In contrast, only about two billion tons CO2 eq/yr are removed from the atmosphere by carbon sequestration in forests and wildlands.

With their warm, waterlogged soils, rice paddies contribute up to 17 percent of global methane emissions. SUSIBA2 rice is the first high-starch, low-methane rice that could offer a significant and sustainable solution to both global poverty and global warming. Image courtesy of Tamago Moffle, Flickr

However, much of this CO2 equivalent is actually from methane, whether from the back-end of cows or from rice paddies. Methane is second only to CO2 as a greenhouse gas, being responsible for about 20% of the global warming effects since pre-industrial times. Atmospheric methane is about 20 times more effective than CO2 at trapping heat, but has a much shorter half-life in the atmosphere than CO2 (about 8 years for methane versus between 30 and 300 for CO2, depending upon decay path).

Rice paddies are the largest anthropogenic methane source and produce over 10% of atmospheric methane. Their warm soggy and nutrient rich soil provides ideal conditions for methanogenesis.

However, there are two competing issues at stake. One is feeding billions of humans, especially the 3 billion new folks coming on board in the next 30 years. The other is protecting the environment. Agriculture has never been particularly friendly to the planet’s ecosystem. Not only does it remove natural habitat, but it takes lots of water and resources away from Nature and degrades the soil over time, not to mention the pesticides and fertilizers.

Rice is at the center of this dilemma. Rice feeds half the world’s population, and is slated to feed even more as the population grows. It is difficult to overstate the importance of this new rice in battling global poverty and global warming.

Jansson points out that, “As the climate warms, rice paddies will produce even more methane, making this technology even more significant.”

In addition to a near elimination of the greenhouse gas methane associated with its growth, SUSIBA2 rice produces substantially more grains for a richer food source. The new strain is shown here (right) compared to the study's control. Image courtesy of Swedish University of Agricultural Sciences

To create the new rice, called SUSIBA2 rice (SUgar SIgnaling in BArley 2), the researchers identified the gene in barley that directs how the plant uses carbon. During photosynthesis, carbon dioxide is absorbed and converted to sugars to feed or to be stored in various parts of the plant. The distribution of sugars is controlled by a special protein, called a transcription factor, that binds to certain genes and turns them on or off.

The researchers started with grains of barley high in starch, then identified the genes that were most active, narrowing down the possibilities until they found the specific transcription factor that regulates the conversion of sugar to starch in the above-ground portions of the plant, particularly the grains or seeds.

In fact, this gene turned out to be a type known as a master regulator. Master regulators control several genes and processes in metabolic or regulatory pathways and it makes sense that such a gene would be able to cause such a huge change in that plant’s chemistry.

They then spliced that gene into common rice. The change shifted the way the rice plant uses the carbon it pulls out of the atmosphere, making the plant send more carbon into growing grain and stems and less into its roots where bacteria convert much of it into methane.

So not only is methane reduced but starch and seed production are increased.

It’s important to note that this is not some Frankengene, but a natural gene in a sister grain, barley, that controls the same metabolic processes that already occur in the rice. Further research is underway to gain a more holistic understanding of any impacts a decrease in methane-producing bacteria may have on the system, but several years of field studies in China have demonstrated that SUSIBA2 delivers increased crop yields and a near elimination of methane emissions with no obvious adverse effects.

Jansson worked closely with Chuanxin Sun of the Swedish University of Agricultural Sciences, who has contributed significantly to the research on rice. Much of the work was done at PNNL’s Environmental Molecular Sciences Laboratory, a DOE user facility specifically built to encourage these types of collaborations. The team published a research paper about the rice in July in Nature, together with other researchers at the Swedish institution and colleagues at China's Fujian Academy of Agricultural Sciences and Hunan Agricultural University.

Combating global warming and global poverty – not bad for a single gene.